Gtp Cyclohydrolase 1-Deficient Dopa-Responsive Dystonia, also known as hereditary progressive dystonia with marked diurnal fluctuation, is related to parkinsonism and dystonia, and has symptoms including torticollis, dystonia, diurnal and gait ataxia. An important gene associated with Gtp Cyclohydrolase 1-Deficient Dopa-Responsive Dystonia is GCH1 (GTP Cyclohydrolase 1). Affiliated tissues include brain, and related phenotypes are intellectual disability and sleep disturbance